The invention relates in general to mortar tubes, and in particular to finless mortar tubes with reduced wall thicknesses.
Mortars tubes presently used by the United States armed forces are generally available in three sizes of nominal inside diameter, namely, 60 mm (millimeter), 81 mm and 120 mm. The current 60 mm and 81 mm mortar tubes have cooling fins that function to reduce the tube temperature during firing. The mortar tube cooling fins are expensive to manufacture and add additional weight to the mortar tube. The 120 mm mortar tube does not have cooling fins because its required rate of fire is less than the 60 mm and 81 mm mortars. Lightweight finless mortar tubes in the 60 mm and 81 mm sizes that are capable of firing high pressure rounds at the high rates of fire characteristic of United States mortars are not known.
Generally speaking, the soldier in the field benefits whenever anything he/she must handle is made to weigh less. In “Hydrostatic Extrusion of 60 mm Mortar Tubes” (Watervliet Arsenal, Watervliet, N.Y., October 1974, available from NTIS, Springfield, Va.), DeFries describes the hydrostatic extrusion of four 60 mm tubes made of Inconel, a “superalloy.” These tubes were relatively thick-walled (approximately 5 mm or greater) and included cooling fins. Although some mechanical tests were performed on the DeFries tubes, it does not appear that the tubes were ever “live-fire” tested. There is a need for a mortar tube that is light in weight (thin-walled), cheap to manufacture (no cooling fins), and capable of rapid, continuous firing without failure.